Asphalt is a solid or viscous, typically semisolid, mixture of hydrocarbons which are amorphous, and the predominant constituents of asphalt are bitumens derived from refinery petroleum. Asphalts and/or bitumens are typically employed for paving, road coatings, roofings, sealing and also for carpet backing, such as a bitumen-backed carpet tile.
Asphalt or bitumen has been employed as a backing layer for carpet material. Such bitumen employed as a backing layer has been modified by the addition of various polymers, for example, styrene-butadiene-styrene block copolymers as well as mixtures of high and low density polyethylene polymers, and by urethane polymers as described more particularly in U.S. Pat. No. 5,096,764, issued Mar. 17, 1992, hereby incorporated by reference. Bitumen used as a backing layer for a carpet material has been modified by employing therein a urethane reaction product composed of a hydroxyl-terminated, long-chain diene hydrocarbon and a polyisocyanate to provide a carpet material which is heat stable during a wet steam process printing operation. The liquid hydroxyl-terminated homopolymers of butadiene employed as the modifying polymers in the bitumen carpet backing layer are commercially sold as Poly-BD.RTM. liquid resins (a trademark of ELF-Atochem SA of Hauts-de-Seine, France), and their use with various polymers and components are described in an advertising brochure "Poly bd.RTM. resins In Urethane Elastomers", also hereby incorporated by reference.
Asphalt or bitumen has a primary use as a moisture barrier for masonry, such as poured concrete, in the construction of commercial and residential buildings wherein a bitumen coating is typically applied to the exterior wall after the concrete foundation has been poured to prevent the penetration of moisture. The use of bitumen coatings as a moisture-protective barrier by itself is difficult, since bitumen tends to be too fluid, therefore usually requiring a backing and also a filler, such as a modified polymer, like the styrene-butadiene-styrene, in order to stiffen the bitumen as a moisture barrier. However, bitumen even with a filler and a styrene-butadiene-styrene copolymer is not satisfactory at normal operating ranges, since at the high temperature end of the application of the bitumen as a moisture barrier, say for example 80.degree. F. to 110.degree. F., the bitumen is too fluid, while at low temperatures, the bitumen exhibits diminished surface tackiness, for example, in the 10.degree. F. to 30.degree. F. range, so that the bitumen does not stick to the masonry it is designed to protect.
Therefore, it is desirable to provide for a new, improved, modified bitumen composition sheet material and method as a moisture barrier in which the modified bitumen sheet material may be employed over a range of temperatures with satisfactory characteristics, such as preventing the passage of moisture, tackiness and flexibility.